C+S May 2021 Vol. 7 Issue 5 (web)

Costa Rica, 15 miles off the Pan American Highway near the town of Punta Morales. The tidal flats between the shore and estuary channel experience high tides on the order of four meters (13 feet), and the alignment of the ship during construction was designed to minimize the launch route’s traverse over shore and shallow waters. “We want this launch to go smoothly,” said Doggett. “This ship will be a flagship Introducing Ceiba The largest wooden vessel under construction in the world now has a name: Ceiba, inspired by a group of tree species native to tropical regions of the Americas and West Africa. Ceiba is the flagship vessel of Sailcargo, an eco-friendly company building zero-emission ships. Ceiba was designed by naval architect Pepijn van Schaik of Manta Marine Design B.V., who also designed Tres Hombres, a smaller cargo ship that Doggett once crewed. When complete, Ceiba will be a three-mast schooner, 45 meters (147 feet) long, with an eight-meter beam, a rigging height of 34 meters. Cargo capacity will be 250 metric tons / 350 cubic meters, plus additional on-deck space. It will be nearly 10 times the size of Tres Hombres. Wood for Ceiba was sourced locally and included trees felled by tropical storms. Frames are Spanish Cedar, which is in the mahogany family and not a true cedar, while the stem and framing are Guapinol, also known as Jatoba. Sailcargo has implemented a planting program to offset timber used. Ceiba will also feature two high-efficiency 120 horsepower electric motors. The variable-pitch propellers will generate power when the ship is under sail by working as underwater turbines to charge batteries and meet onboard electrical needs. Since routes will include equatorial regions, solar will also be added. Sailcargo is not saying that wind power would be a practical replacement for all fossil- fuel-based-seaborne commerce. But it can provide another option and there is a growing demand for such alternatives. Companies with environmentally friendly and carbon neutral products can now complete the supply chain by offering zero-emission marine delivery. Sailcargo believes successful businesses must follow the basic tenet of providing what customers want.

for the country and a source of national pride. The president [of Costa Rica] is expected to be at the launch.” Macrae identified several challenges in developing an accurate 3D model of the launch route. “The water is shallow for several hundred yards, even at high tide, and there are a lot of unknowns about the bottom of the channel, such as how much is sand, mud or silt,” he said. The solution was a mix of old school and high tech. Macrae and a Sailcargo team rowed into the estuary and put lead lines over the side for soundings. “We had the R10 in the boat and took sag measurements to come up with an offset. The horizontal positions were very tight, and we logged the soundings.” The team captured sound- ings in areas close to shore to allow cross-validation with laser scan data of the exposed mudflats. Macrae wanted to include local control for the soundings and site survey, but there were many unknowns, such as origins of existing marks found on site, and lack of published values or reference frame- work (datums). “It was easy to determine the average high tide, so we decided to establish values for the control and reference everything to that, including our soundings and tide values.” Macrae chose three existing survey marks around the shipyard and performed static observations with his R10. He processed the data in Trimble Business Center (TBC) against a continuously operating refer- ence station (CORS) 5km away and produced average horizontal un- certainty of 10 mm (95 percent confidence) for all three marks. Macrae confirmed the results via a three-point resection using the one-second SX10, generating residuals of 8 mm. The resulting coordinate frame- work was used for all the sounding, topographic and scan work going forward. “Since I had two R10 receivers, I could be very efficient,” Macrae said. “While the static observations were underway I started an RTK job in the same datalogger project with the second receiver and walked the shipyard picking up points of interest.” Macrae also used the SX10 to scan areas of the riverbed exposed at low tide. Using it as a total station, he back-sighted his local control and then scanned. “At low tide, I took the SX10 out about fifty yards from shore with my local control still visible. I did a full dome scan at each setup, collecting millions of observations of the river bottom. Because I was using existing control, the point clouds were automati- cally georeferenced to the rest of my data.” The dense point cloud was combined with the manual soundings, RTK, and optical observations to create an accurate 3D model of the launch route. “We realized errors could creep into the model from the sound- ings, so scanning provided a good check,” he said. Macrae then created several color-coded plan views with best and worst-case scenarios. Because the density of the ship has not yet been determined, he used a range of values for Ceiba’s final displacement. Doggett said the results of the soundings and scanning were welcome as they confirmed that the alignment was good, and the launch route accurate. Both the launch route across the ground and the shallow flats will be lined with logs to the point where the ship can float on its own.


may 2021


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